class_docstr: Domain for Neural Network architectures. 
docstr: Returns a string representation. 
docstr_tok: ["Returns","a","string","representation","."]
code: def __str__(self):
      """Returns a string representation."""
      cc_attrs = {
          key: getattr(self.constraint_checker, key)
          for key in self.constraint_checker.constraint_names
      }
      return "NN(%s):%s" % (self.nn_type, cc_attrs)
  
imports: import numpy
  from copy import copy
  from ..exd.domains import Domain
label_desc: Use image node_id 6 for calling the NNDomain obj's underlying member method code with example usage: obj.__str__() and returns: unknown